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Essay On Pathophysiology Of Epilepsy

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Pathophysiology Of Epilepsy
Neuronal messages are transmitted by electrical impulses called the Action Potential. This is actually a net positive inward ion flux that leads to depolarization or voltage change in the neuronal membrane. The ions involved include sodium, potassium, calcium and chloride. Normally brain tissues prevent hyper excitability by several inhibitory mechanisms involving negative ions like chloride ions.
There are two types of transmission of impulses - excitatory and inhibitory. Excitatory transmission involves Glutamate that is the principal excitatory neurotransmitter in the brain. GABA or Gamma amino butyric acid is the principal inhibitory neurotransmitter in the brain.
There are two groups of glutamate receptors - …show more content…

These abnormally discharging epileptic neurons recruit adjacent neurons or neurons with which they are connected into the process. A clinical seizure occurs when the electrical discharges of a large number of cells become abnormally linked together, creating a storm of electrical activity in the brain. Seizures may then spread to involve adjacent areas of the brain or through established anatomic pathways to other distant areas.
On a fundamental level, seizures can be viewed as resulting from an imbalance between excitatory and inhibitory processes in the brain. Proposed mechanisms for the generation and spread of seizure activity within the brain include abnormalities in the membrane properties of neurons, changes in the ionic micro environment surrounding the neuron, decreased inhibitory neurotransmission which is primarily by gamma-amino butyric acid (GABA), or enhanced excitatory neurotransmission which is primarily mediated by the acidic amino acid, …show more content…

The synchronized bursts from a sufficient number of neurons result in a so-called spike discharge on the EEG. At the level of single neurons, epileptiform activity consists of sustained neuronal depolarization resulting in a burst of action potentials, a plateau-like depolarization associated with completion of the action potential burst, and then a rapid repolarization followed by hyperpolarization. This sequence is called the paroxysmal depolarizing shift. The bursting activity resulting from the relatively prolonged depolarization of the neuronal membrane is due to influx of extracellular Ca++, which leads to the opening of voltage-dependent Na+ channels, influx of Na+, and generation of repetitive action potentials. The subsequent hyperpolarizing after potential is mediated by GABA receptors and Cl− influx, or by K+ efflux, depending on the cell type.
Summary Of Mechanism of seizure formation
• Excitation of a group of nerves. This is caused by inward currents of Na, Ca and involvement of excitatory neurotransmitters like Glutamate and Aspartate.
• Too little inhibition.
• Epileptogenesis and hyperexcitability and hypersynchronization of neurons that facilitates spread. There has to be abnormal synchronization – a property of a population of neurons to discharge together independently. Alone, a hyperexcitable neuron

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